CVE-2026-57857

Flow Payment Plugin for WordPress Reflected Cross-Site Scripting via error_message Parameter

MEDIUM
4.3
CVSS Score
Published: July 18, 2026 at 08:33 PM UTC
Updated: July 23, 2026 at 09:12 PM UTC
1 product affected across 1 vendorFlow Payment

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Severity
MEDIUM4.3
Exploit prediction
EPSS 0.3%
SSVC
No known exploit

Description

The Flow Payment plugin for WordPress (flow.cl) version 3.0.8 is vulnerable to reflected cross-site scripting on the WooCommerce checkout page. When the plugin handles an order cancellation, the error_message GET parameter is passed directly to wc_add_notice() in flowpayment-fl.php (lines 57-58) without input sanitization (for example sanitize_text_field()) or output escaping (for example esc_html()) before being rendered in the checkout notice HTML. An unauthenticated attacker can craft a URL containing a JavaScript payload in the error_message parameter (for example /checkout/?add-to-cart={product-id}&cancel_order=true&error_message={payload}); when a victim with an active WooCommerce checkout session follows the link, the payload executes in the victim's browser in the origin of the WordPress site.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Flow Payment· Flowwordpress-plugin
60%
v ≤ 3.0.8
Vendor states this is fixed in 3.0.9 (unaffected)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

4.3MEDIUMVulnCheck
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
LOW
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-79

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